what happened top kevin collins? kpix 5 reporter joe vazquez tells us that this man may have taken the secret to his grave. >> reporter: in 1984, police were investigating the most high-profile missing child case in a generation. it turns out a neighbor of kevin collins had a sordid past. wayne jackson had a record that involved child molestation. he also had a black dog, just like the man kevin was last seen talking to. >> this case is a case that haunts the san francisco police department. >> reporter: now, 29 years later, police chief greg suhr is revealing for the first time that jackson is a person of interest in the case. but why wasn't he arrested back then? >> he was detained. he was interviewed. he allowed a consent search of the same house we just did a search warrant on. a photo spread was shown to the two witnesses that described the suspect. they weren't able to pick him out of the photo spread. >> they knew enough about his past. they dropped the ball on this guy. >> reporter: mark glass, an advocate fo